Method of servicing underground liquefied petroleum gas tanks during cold weather



@et 3.9, E943. L J, WHITE Zlg METHOD 0F SERV ICING UNDERGROUND LIQUEFIED PETROLEUM GAS TANKS DURING COLD WEATHER Filed Jan. 11, 1940 WATER g Patented Oct. 19, 1943 LIQUEFIED PETROLEUM DURING COLD WEATHER Gas TANKS y Loyd J. White, San Antonio, Tex., assignor to Southern Steel Company, San Antonio, Tex., a corporation of Texas Application January 17, 1940, Serial No. 314,311

Claims.

This invention relates to a method of servicing underground liqueiied petroleum gas storage A tanks for generating and dispensing liqueed petroleum gases and, among other objects, aims to provide an improved method of pre-heating the liquefied gas in a service truck tank and delivering it under pressure to an underground storage tank during extremely cold weather at a temperature well above the atmospheric temperature and the initial boiling point of the liqueed gas. The idea is to service such under-` ground tanks with blends of liquefied petroleum gases consisting principally of butane and propane and which blends may have an initial boiling point as low as 0 F. at atmospheric pressure. It should be understood that such liquefied gases are stored under pressure ink underground tanks It will be understood that such tanks are usuburied below the frost line and therefore absorb heat from the surrounding earth. The idea is to maintain the temperature' of the liquefied gas in a service truck tank well above that of the atmospheric temperature and preferably above that existing in the underground tank. so that an underground tank may be serviced with such pre-heated fuel during the coldest weather without interrupting the gas service; that is to say, the temperature'of the filling charge will be well above its initial boiling point when delivered into the underground tank and will va- Y porize readily.

Fig. 2 is an enlarged sectional view taken on theline2-2ofFlg.1;and

Fig. 3 is an en larged fragmentary sectional. view of an exhaust control valve taken on'the line I-I of Fig. 2.

carbon constituents, the boiling point of which is, say 0 F. or higher at atmospheric pressure.

ally serviced by a service truck tank. In parts of the country where atmospheric temperatures range from, say 10-to 30 below zero, Fahrenheit, during portions of the winter months, it will readily be seen that the temperature of the liquefied gas in ordinary truck tanks will always be approximately the saine as that of the atmosphere, say 20 F., for example. If the cold liquefied gas is pumped into an underground storage tank or container, it will not vaporize until it absorbs sumcient heat from the earth or from a supplemental vaporizer. or both, to raise the-temperature above the boiling point at the pressure existing in the underground tank. In fact, the cold incoming liquefied gas will condense the vapor in the underground tank very rapidly and thereby interrupt the supply of gas or vapor delivered through the service pipe. To supply the necessary heat rapidly to the cold Vliquefied gas and overcome this diiculty would imposea heavy load on any type of artificial heat exchanger. Moreover, it might require several hours for the ordinary underground tank to absorb sufficient heat from the earth to raise the temperature of the new charge of liquefied gas to make it vaporize. 'In accordance withv the present invention,'this serious difilculty is overcome by pre-heating the liquefied gas in a serv- Referring particularly to the drawing and to the improved method, the present invention relates to underground'liquetied petroleum gasl systems of the'general type disclosed in Patent No. 2,121,675 and copending application Ser. No. 280,210, led June 20, 1939, wherein an under-` ground tank i0 is buried in the ground below the frost line in heat exchanging relation with the surrounding earth to absorb vaporizing heat therefrom and insure a continuous supply of gas.

, The hydrocarbon fuel used in such systems usually Aconsists of blends of butane, propane, isobutane and other more or less volatile hydroice truck tank and keeping it at a temperature of 50 F. orV more, and preferably above vthat'existing in the underground tank.

Referring more particularly to the illustrated apparatus, which is designed to carry out the improvedmethod, the underground storage tank I0 is shown as having a supplemental water heat exchanger Il of the same type as that ydisclosed 40' in'my copending application Ser. No. 276,024, filed May 26, 1939... Herein, the system may be like that disclosed in the aforesaid Patent No. 2,121,675, but it is shown for. convenience as being substantially the same as the one disclosed in the aforesaid application Ser. No. '280,210, which is adapted to be pressure filled and which delivers the gas in the gaseous phase from the storage tank. However, it is to -be understood that the system may be of any of the types covered by several of my copending applications and patents.V As shown in the aforesaid application Ser. No. 280,210, gas is delivered from the tank i0 through a stand-pipe l2, a unitary valved tting i3, a pressure reducing regulator i4 and the fitting I3 and outwardly .from a protecting casing IB having the usual cover I1. Both the service pipe and the tank are arranged well below the frost line, as indicated.

A service truck I8 having the .usual pressure tank I9 is shown as being connected to fill the underground tank. In this instance, the service truck tank is shown as being covered with insulation and has a heating passage conveniently formed by structural channel 2l welded longitudinally along its bottom wall so that exhaust gas from the truck motor 22 can be di' verted to and through the passage to heat the liquefied gas in the tank. However, any other suitable source of heat may be used. Herein, a branch exhaust conduit 23 is connected to the usual exhaust conduit 24 and is shown as having a controlling valve 25 adapted to be operated from the truck cab in any convenient manner. The by-passed gas passes through the channel 2| and exhausts through a conduit o-r tail pipe 25 at the rear end of the truck. The insulation of the tank is suiiicient to prevent rapid transfer of heat therefrom and the arrangement is such that the temperature in the tank may be maintained at all times well above the boiling point of the liquefied gas during the coldest weather while the truck motor is running.

The liquefied gas in the truck tank is shown as being delivered through an outlet pipe 21, a pump 28 and a hose 29 connected to the usual filling valve on the fitting I3. The pipe sections, fittings and the hose 29 are also well insulated to prevent dissipation of heat from and consequent cooling of the liquefied gas. The

itank I9 has a removable vented cover 30 for the conventional filling, safety and gauging appurtenances and this cover is also preferably insulated as shown.

In an underground system of this type, the average temperature of the contents of the tank, due to the temperature of the surrounding earth below the frost line. is around 50 F. to 55 F. The temperature maintained in the service truck tank will preferably be 55 F. or higher, to prevent cooling the stored liquefied gas and, consequently, interrupting the house service. This also avoids the possibility of imposing a heavy heating load on the water heat exchanger II and freezing the water in it. It will be understood that all of the exhaust gas from the truck motor may be continuously by-passed through the truck tank heating passage during extremely cold weather. The control valve will, of course, be regulated according to the temperature or vapor pressure in the truck tank. If necessary, other sources of heat may be employed to supplement the heat of the exhaust gas.

Obviously, the present invention is not restricted to the particular steps of the method herein described. Furthermore, the apparatus is capable of a wide variety Aoi! modifications.

What is claimed is:

1. That method of servicing underground liquefied petroleum gas storage and generatingl tanks, during extremely cold weather, with hyf drocarbon fuel having a boiling point above the atmospheric temperature, which consists in preheating the liquefied gas in a service truck tank and pumping the pre-heated liquefied gas from the truck tank into the underground tank at a temperature approximating that of the normal temperature of the earth surrounding the-underground storage tank and without reducing the temperature between the truck tank and the underground tank.

2. That method of servicing underground liquefied petroleum gas storage and generating tanks during extremely cold weather using hydrocarbon fuel having a boiling point above the atmospheric temperature, which consists in preheating the liquefied gas in a service truck with exhaust gas from the truck motor during extremely cold weather to approximately the boiling temperature at the pressure of the liquefied gas in the underground tank; and pumping the pre-heated liquefied gas into the underground tank without reducing its temperature to prevent chilling the contents of the storage tank and interrupting the supply of generated gas.

3. That method of servicing underground liquefied petroleum gas storage and generating tanks using hydrocarbon fuel which has to absorb vaporizing heat from the earth, which consists in heating a charge of the liquefied gas under pressure in transit during extremely cold weather to such temperature that it will immediately begin to vaporize at the temperature and pressure in the underground tank; and delivering the heated charge into the underground tank without reducing its temperature whereby to maintain a continuous supply of generated gas during the filling operation.

4. The method of servicing an underground liquefied hydrocarbon gas storage and generating tank during extremely cold weather with liquefied hydrocarbon fuel having a boiling point above the cold weather temperature, which comprises transporting the fuel in an insulated container from a source of supply to the vicinityof the tank, heating said fuel during said transportation, and` transferring said fuel directly from the container to the tank at approximately the temperature of the fuel at the point of discharge from the container.

5. That method of servicing liquefied petroleum gas storage and generating tanks, which are buried in the ground to absorb vaporizing heat from the surrounding earth, with hydrocarbon fuel having a boiling point above the atmospheric temperature in extremely cold weather, which comprises transporting the fu'el in a gas-'tight service truck tank from a source of supply to the vicinity oi' the undergrougid tank; heating the fuel While in transit by h at derived from the truck motor to a temperature approximating that of the liquefied gas in the underground tank; and pumping the heated fuel into the underground tank without appreciably reducing its temperature, and at a pressure exceeding that existing in the underground tank, to prevent chilling of the contents of the underground tank and thereby insure a continuous supply of generated gas from the underground tank during the filling operation.

LOYD J. WHITE. 

